Z‐ligustilide ameliorated ultraviolet B‐induced oxidative stress and inflammatory cytokine production in human keratinocytes through upregulation of Nrf2/HO‐1 and suppression of NF‐κB pathway

Ultraviolet B (UVB), a harmful environmental factor, is responsible for a variety of skin disorders including skin inflammation through reactive oxygen species (ROS) and inflammatory mediator production. Here, we investigated the effect of Z‐ligustilide (Z‐lig), an active ingredient isolated from the medicinal plants Cnidium officinale and Angelica acutiloba, on UVB‐induced ROS generation and inflammatory mediator production in normal human epidermal keratinocytes (NHEKs) as well as its underlying mechanisms. Z‐lig significantly rescued UVB‐induced NHEKs damage in a dosage‐dependent manner. Pretreatment of NHEKs with Z‐lig inhibited UVB‐induced ROS production in NHEKs. Both silencing the nuclear factor E2‐related factor 2 (Nrf2) and the supplement of tin protoporphyrin IX (SnPP), a haeme oxygenase‐1 (HO‐1) inhibitor, cancelled the inhibitory effect of Z‐lig on UVB‐induced ROS upregulation in NHEKs. Moreover, pretreatment of NHEKs with Z‐lig reduced UVB‐induced nuclear factor kappa B (NF‐κB)‐dependent inflammatory mediators (IL‐6, IL‐8 and MCP‐1) production at both mRNA and protein level. In the presence of Z‐lig, UVB‐induced NF‐κB subunit p65 nuclear translocation was abolished, and the IκBα degradation was suppressed. Taken together, these findings suggest that Z‐lig can suppress UVB‐induced ROS generation through Nrf2/HO‐1 upregulation and inflammation by suppressing the NF‐κB pathway, suggesting that Z‐lig may be beneficial in protecting skin from UVB exposure.     

Baicalein inhibits matrix metalloproteinase 1 expression via activation of TRPV1‐Ca‐ERK pathway in ultraviolet B–irradiated human dermal fibroblasts

Increased matrix metalloproteinase 1 (MMP‐1) expression is a feature of photo‐aged skin. We investigated the effects of baicalein and sulphoraphane on ultraviolet B (UVB) irradiation–induced MMP‐1 expression and apoptosis using human dermal fibroblasts. UVB irradiation not only increased MMP‐1 expression, but also caused apoptosis. Both baicalein and sulphoraphane protected cells from UVB irradiation–induced apoptosis, but only baicalein inhibited MMP‐1 expression. UVB irradiation activated 12‐lipoxygenase, and its product, 12‐hydroxyeicosatetraenoic acid, activated TRPV1 channels. The resulting UVB irradiation–induced Ca²⁺ increase was blocked by the 12‐lipoxygenase inhibitor baicalein and the TRPV1 blocker capsazepine, but not by the Nrf2 inducer sulphoraphane. UVB irradiation also increased ROS generation and decreased Nrf2 protein levels. UVB irradiation–induced MMP‐1 expression was blocked by the Ca²⁺ chelator BAPTA, by capsazepine and by TRPV1 silencing. However, induction was unaffected by the antioxidant N‐acetylcysteine. ERK phosphorylation and JNK phosphorylation were induced by UVB irradiation, but only ERK phosphorylation was Ca²⁺ sensitive. Increased MMP‐1 expression was blocked by PD98059, but not by SP600125. Thus, increased MMP‐1 expression is mediated by increased cytosolic Ca²⁺ and ERK phosphorylation. UVB irradiation–induced ROS generation is also Ca²⁺ sensitive, and UVB irradiation–induced apoptosis is caused by increased ROS. Thus, baicalein, by blocking the UVB irradiation–induced cytosolic Ca²⁺ increase, protects cells from UVB irradiation–induced MMP‐1 expression and apoptosis. In contrast, sulphoraphane, by decreasing cellular ROS, protects cells from only UVB‐induced apoptosis. Thus, targeting 12‐lipoxygenase may provide a therapeutic approach to improving the health of photo‐aged human skin.     

Improved detection of lacZ reporter gene expression in transgenic epithelia by immunofluorescence microscopy

The bacterial lacZ gene is commonly used as a reporter for the in vivo analysis of gene regulation in transgenic mice. However, several laboratories have reported poor detection of beta-galactosidase (the lacZ gene product) using histochemical techniques, particularly in skin. Here we report the difficulties we encountered in assessing lacZ expression in transgenic keratinocytes using classic X-gal histochemical protocols in tissues shown to express the transgene by mRNA in situ hybridization. We found that lacZ reporter gene expression could be reliably detected in frozen tissue sections by immunofluorescence analysis using a beta-galactosidase-specific antibody. Moreover, we were able to localize both transgene and endogenous gene products simultaneously using double-label immunofluorescence. Our results suggest that antibody detection of beta-galactosidase should be used to verify other assays of lacZ expression, particularly where low expression levels are suspected or patchy expression is observed.     

Nrf2蛋白在中波紫外线照射HaCaT细胞中的光保护作用

【摘要】 目的 探讨Nrf2对中波紫外线（UVB）致HaCaT细胞光损伤的保护作用及其作用机制。方法 将培养的HaCaT细胞分为对照组、UVB组、Nrf2组、Nrf2 + UVB组，Nrf2组、Nrf2 + UVB细胞感染Nrf2基因过表达慢病毒，UVB组、Nrf2 + UVB组细胞以30 mJ/cm2的UVB照射30 s，继续培养24 h，观察UVB照射后HaCaT细胞形态的变化，Western印迹检测各组Nrf2蛋白水平，CCK8法检测各组细胞生存率，流式细胞仪检测各组细胞活性氧（ROS）水平，生化法检测超氧化物歧化酶（SOD）水平。多组间均数比较采用单因素方差分析，组间两两比较采用LSD-t检验。结果 对照组 HaCaT 细胞形态为多角形、呈簇集状生长，UVB照射后细胞出现皱缩、变圆，漂浮细胞数增多，贴壁数量明显减少。对照组、UVB 组、Nrf2组、Nrf2 + UVB组Nrf2蛋白相对表达水平分别为1.84 ± 0.047、0.63 ± 0.082、2.19 ± 0.168、1.43 ± 0.069，差异有统计学意义（F = 64.81，P < 0.05），Nrf2组水平高于对照组（t = 14.82，P < 0.05）；4组细胞生存率分别为98.00% ± 2.39%、24.40% ± 2.98%、71.63% ± 3.39%、43.38% ± 3.39%，差异有统计学意义（F = 236.66，P < 0.05），UVB 组细胞活力低于对照组（t = 33.34，P < 0.05）和Nrf2 + UVB组（t = 10.07，P < 0.05）；4组细胞的相对ROS含量分别为1.27 ± 0.10、5.65 ± 0.19、2.10 ± 0.73、3.67 ± 0.19，差异有统计学意义（F = 481.39，P < 0.05），UVB组高于对照组（t = 33.68，P < 0.05）和Nrf2 + UVB组（t = 12.47，P < 0.05）。4组细胞SOD水平差异有统计学意义（F = 170.76，P < 0.05），UVB组低于对照组（t = 11.25，P < 0.05）和Nrf2 + UVB组（t = 17.52，P < 0.05）。4组细胞IL-6水平差异有统计学意义（F = 532.34，P < 0.05），UVB 组高于对照组（t = 28.48，P < 0.05），Nrf2 + UVB组低于UVB 组（t = 27.82，P < 0.05）。4组细胞TNF-α水平差异无统计学意义（F = 2.02，P = 0.19）。结论 Nrf2可以通过降低细胞内ROS水平，提高内源性抗氧化酶SOD的活性，保护细胞免受UVB照射引起的氧化损伤。     

Keratinocyte gene therapy: cytokine gene expression in local keratinocytes and in circulation by introducing cytokine genes into skin

Using the plasmid DNA injection method, we introduced cytokine genes into skin to determine whether systemic expression of cytokine genes is possible. Eight human cytokine [interleukin-4 (IL-4), IL-6, IL-10, transforming growth factor beta1 (TGF-beta1), monocyte chemotactic and activating factor (MCAF), granulocyte-macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma)] gene expression vectors were constructed and injected into rat skin. Transgenic cytokines in local keratinocytes and in the sera were assayed with ELISA. Our results showed that transgenic cytokines were markedly increased in keratinocytes at the injection site. The serum concentrations of IL-4, 6, 10 and TauGF-beta1 reached levels high enough to have systemic biologic effects. However, other cytokines used in this study could not be detected in the sera. Moreover, the serum transgenic IL-10 level after subcutaneous injection was significantly higher than after intramuscular injection. We suggest that keratinocytes can be used as a bioreactor to achieve systemic expression of cytokine genes by DNA injection, but the transgenic protein level in circulation depends on different kinds of cytokine. This level also depends on different target cells used for gene transfer.     

Nrf2-Keap1系统防御紫外线致皮肤光损伤的研究进展

紫外线照射是致皮肤光损伤的重要因素,与其可诱导产生过量的活性氧族有关。核转录相关因子是调节抗氧化应激反应的重要转录因子,Kelch样ECH联合蛋白1是其特异性受体,在紫外线照射等氧化应激情况下核转录相关因子被激活,并与Kelch样ECH联合蛋白1解离进入胞核,启动抗氧化反应元件调控的Ⅱ相酶及抗氧化酶基因的表达,防御紫外线照射所致皮肤光损伤。多种核转录相关因子激活剂对紫外线照射所致皮肤光损伤有潜在的防御作用。     

Intercellular pathway through hyaluronic acid in UVB‐induced inflammation

Ultraviolet B (UVB) radiation induces inflammation in the skin specifically at the site of exposure. We unexpectedly found that UVB‐induced inflammation was not induced in gp91phox‐depleted mice. To test whether gp91phox is directly involved in UVB‐induced inflammation, neutrophil‐ and hyaluronic acid–depleted mice were also irradiated and examined for their response. Hyaluronic acid–depleted mice showed strongly inhibited UVB‐induced inflammation, but the neutrophil‐depleted mice did not exhibit any suppressed UVB‐induced inflammation. To elucidate the pathway by which UVB irradiation induced inflammation, we examined the expression of nucleotide‐binding domain, leucine‐rich‐containing family, pyrin domain‐containing‐3 (NLRP3) and caspase‐1 in the mouse skin. An increase in the expression of NLRP3 and caspase‐1 was seen following the UVB irradiation of C57BL mice; however, the UVB‐irradiated gp91phox‐knockout (gp91phox^?/?) mice did not have this increase in expression. Furthermore, the plasma IL‐1β level increased after the UVB irradiation in C57BL mice, but there was no change in the gp91phox^?/? mice. These results clearly indicate that nicotinamide adenine dinucleotide phosphate oxidase is activated by gp91phox, which is expressed on the surface in response to the increased expression of hyaluronic acid induced by UVB irradiation, and as result, the generation of reactive oxygen species (ROS) increases. This ROS activate NLRP3, and NLRP3 leads to the production of caspase‐1, which subsequently increases IL‐1β, thereby finally inducing inflammation. It is thought that this system may play an important role in the damage and ageing of skin, and further studies are necessary to confirm these finding.     

Ultraviolet light induces Stat3 activation in human keratinocytes and fibroblasts through reactive oxygen species and DNA damage

Please cite this paper as: Ultraviolet light induces Stat3 activation in human keratinocytes and fibroblasts through reactive oxygen species and DNA damage. Experimental Dermatology 2010; 19: 654–660. Abstract: Stat3 is activated by the outer stressors, such as ultraviolet (UV) exposure. In this study, we investigated the Stat3 response to UV irradiation in human epidermal keratinocytes and dermal fibroblasts. Results indicated that UVB and UVC differentially activate Stat3 in these cells. The UV‐induced Stat3 activation was mediated by both reactive oxygen species (ROS) and DNA damage, and the dominancy of ROS and DNA damage to activate Stat3 depended on the wavelength of UV. By using fibroblasts from a patient with xeroderma pigmentosum A (XP‐A) and those transfected with human XPA gene, we found that UVB activates Stat3 via both ROS and DNA damage, while UVC does so mainly via DNA damage. The present data suggest that Stat3 activation in UV‐exposed human skin is one of the initial events where DNA damage and ROS are involved.     

Alterations of immune functions in barrier disrupted skin by UVB irradiation

BACKGROUND: While immunologic events elicited by acute barrier disruption or UVB irradiation have been studied in detail, the biological sequel of multiple insults to the skin is not well understood. OBJECTIVE: Since the skin would receive a variety of simultaneous stimuli in daily life, we tested the effects of sequential treatments with barrier disruption and UVB exposure on skin immunity. METHODS: Earlobes of BALB/c mice received tape-stripping and subsequently low-dose UVB exposure. Control mice were treated with either tape-stripping or UVB. The expression of surface markers and cytokine production in Langerhans cells and keratinocytes and the elicitation response of contact hypersensitivity were compared. RESULTS: By flow cytometry, tape-stripping augmented the expression of MHC class II, CD54, CD80, CD86 and CD40 on Langerhans cells, whereas UVB decreased the expression of some of these molecules. Combination of tape-stripping and UVB induced largely intermediate levels between these two. Upon stimulation with L cells expressing CD40L, Langerhans cells from tape-stripped and UVB-irradiated earlobes strongly transcribed mRNA for interleukin-1beta compared to each treatment. In keratinocytes, tape-stripping or UVB slightly upregulated tumor necrosis factor-alpha and interleukin-1alpha production at both mRNA and protein levels, whereas these two treatments synergistically increased the production of these cytokines. The in vitro hapten-presenting ability of Langerhans cells to trinitrophenyl-immune lymph node T cells ranked first in tape-stripping, second in tape-stripping plus UVB and third in UVB, and so did the intensity of elicitation responses in contact hypersensitivity to a hapten, picryl chloride. CONCLUSION: It is suggested that barrier disruption and UVB antagonize with each other in contact hypersensitivity as a reflection of their effects on Langerhans cell antigen-presenting function, but they synergize in cytokine production by both Langerhans cells and keratinocytes.     

Z‐Ligustilide inhibits benzo(a)pyrene‐induced CYP1A1 upregulation in cultured human keratinocytes via ROS‐dependent Nrf2 activation

Benzo(a)pyrene (BaP), a polycyclic aromatic hydrocarbon (PAH), is an environmental contaminant that can induce cytochrome P4501A1 (CYP1A1) upregulation via aryl hydrocarbon receptor (AhR) activation and provoke inflammation. Here, we investigated the effect of Z‐Ligustilide, an active ingredient isolated from the medicinal plants Cnidium officinale and Angelica acutiloba, on BaP‐induced CYP1A1 upregulation in normal human epidermal keratinocytes (NHEKs) as well as its underlying mechanisms. Z‐Ligustilide significantly inhibited BaP‐induced CYP1A1 upregulation in NHEKs. Treatment of NHEKs with Z‐Ligustilide induced Nuclear factor‐E2‐related factor 2 (Nrf2) nuclear translocation and expression of the Nrf2‐regulated genes for haeme oxygenase‐1 (HO‐1) and NAD(P)H:quinine oxidoreductase‐1 (NQO1). AhR silencing, SB203580 (a p38 inhibitor), SP600125 (a JNK inhibitor), U0126 (a MEK inhibitor) and LY294002 (a PI3K inhibitor) did not suppress Z‐Ligustilide‐induced Nrf2 activation. Moreover, treatment of NHEKs with Z‐Ligustilide increased reactive oxygen species (ROS) and L‐N‐acetylcysteine (L‐NAC, an antioxidant) attenuated Z‐ligustilide‐induced Nrf2 nuclear translocation and HO‐1 expression. L‐NAC or knock‐down of Nrf2 significantly attenuated the inhibitory effects of Z‐Ligustilide on BaP‐induced CYP1A1 upregulation in NHEKs. Taken together, these findings suggest that Z‐Ligustilide can suppress BaP‐induced CYP1A1 upregulation through ROS‐dependent Nrf2 pathway activation and may be beneficial in preventing or treating BaP‐induced skin damage.     

Microarray analysis of UVB-regulated genes in keratinocytes: downregulation of angiogenesis inhibitor thrombospondin-1

BACKGROUND: Ultraviolet (UV) B light is an environmental mutagen that induces changes in cutaneous gene expression leading to immune suppression and carcinogenesis. Keratinocytes are a primary target for UVB. OBJECTIVE: To further delineate UVB-induced gene expression changes in keratinocytes. METHODS: cDNA microarray technology was utilized to examine gene expression in normal human KC (NHKC) following 20 mJcm(-2) UVB irradiation. Data was confirmed by semi-quantitative RT-PCR. RESULTS: Microarray analysis revealed 57 genes were upregulated, and 27 genes were downregulated, by at least two-fold following UVB. One downregulated gene was the endogenous angiogenesis inhibitor thrombospondin-1 (TSP-1). Semi-quantitative RT-PCR confirmed persistent downregulation of TSP-1 up to 18h following UVB. Microarray analysis also revealed upregulation of platelet-derived endothelial cell growth factor (PD-ECGF)--an angiogenesis activator. CONCLUSION: Our results suggest a gene expression mechanism by which UVB induces an angiogenic switch in keratinocytes. This may represent an important early event promoting neovascularization and growth of cutaneous neoplasms.